In the stiffening of flexible materials such as shoe parts a method has been developed in which molten synthetic polymeric material is applied to a surface of a part to be stiffened, such as the toe portion of a shoe, in wetting adhesive relation and thereafter is cooled to a stiff resilient condition providing the desired stiffness.
In a modification of that method particularly useful for stiffening of workpieces having surface irregularities and/or openings, the molten resin material is deposited on a chilled transfer surface member and pressed against the surface of the article to be stiffened while the exposed surface of the resin on the transfer surface member is still in condition effective to wet and adhere to the surface of the article to be stiffened. The transfer surface member is refrigerated to bring its temperature well below room temperature, often to 5.degree. C. and hardens the resin adjacent it to enable the transfer surface member to be separated cleanly from the resin which adheres to the workpiece.
While these methods have provided effective stiffening and have gone into extensive commercial use, the stiffener layers formed have not had the strength required for certain types of shoes particularly men's shoes. Efforts have been made to provide greater stiffness through the use of stiffer resins. However, with the modified method, it has been found that the chilled transfer surface members would not strip cleanly from stiffener material deposited on the workpiece but rather that the resin adjacent the transfer surface member would become gummy and rubbery and would adhere to the transfer surface member under the operating conditions required in commercial operation as in shoe factories.